The present invention relates to a symbol plate for an artillery collimator and an artillery gun sight, said plate having symbols, arranged in a row, symmetrically in relation to a vertical center line across the plate, said symbols indicating the distance to the center line.
For the control and adjustment of the zero position of artillery guns an artillery collimator is used. It comprises a lens system (similar to a photo objective, but better), in the focal plane of which a translucent symbol plate is located. In the sight of the gun a similar symbol plate is located. Angles defined by the distances of the symbols from the optical axis must be exactly equal in both instruments.
Upon firing the gun is usually displaced a few decimeters forwards or backwards, which does not affect the alignment. It is, on the other hand, necessary to observe whether the gun then has performed an angular movement, and in such case correct this on the side scale of the sight. FIG. 1, illustrates the situation. The collimator is positioned 10 to 20 meters from the gun, and directed with its tracking telescope towards the sight of the gun. The person aiming the gun sees the collimator objective in his sight as a small bright disc and one or more symbols S.sub.1 therein. He aims the sight until these marks coincide with the corresponding symbols S'.sub.1 on the aiming plate of the sight (FIG. 1a). After the firing, in the case where the gun has rotated, the person aiming sees another symbol S.sub.n, which covers a symbol S'.sub.n in the sight (FIG. 1b). He then turns the sight, until the symbol S.sub.n covers the corresponding symbol S'.sub.n on aiming plate of the sight. The gun is then again positioned in the correct angular position (FIG. 1c).
The collimator is usually placed at a distance of 10 to 20 meters from the gun, which means that its objective must be provided with a diameter of 70 to 80 mm in order to be observable as a bright disc with 4 mrad diameter at 20 meters. If it then is desirable to see 1.5 to 2 symbols in this disc, their dimension must be about 2 mrad. Since the sight of an artillery gun usually has a four times magnification, the image of the symbols in the ocular will be about 8 mrad, which can be considered to be sufficient for troublefree reading.
If it is presumed that the gun moves .+-.1 meter as a maximum, the row of symbols (at a distance of 10 meters between the collimator and the sight) must be about .+-.100 mrad (milliradians) long as between 50 and 100 symbols are required in each direction counted from the vertical symmetry plane (center of aiming plate--optical axis). These symbols must be easily readable, must not give the slightest possibility of confusion, must give information about whether just the symbol in sight is located to the right or to the left of the axis, and the distance to said axis. The device must be quite usable even for weary staff in stress condition.
Up to the present designed symbol rows consisting of letters have been used (see FIG. 2b), but since the alphabet is not sufficient, certain letters have been turned upside down or reversed. Letters or digits can be combined or purely imaginary figures can be used. There is a risk that such a symbol system causes wrong aiming, accidents and possibly renders this system unusable in practice.
Accordingly, it is an object of the present invention to provide a symbol plate which facilitates adjustment of the sight.
Another object is to provide such a symbol plate which provides unique, easy to read, easy to understand and easy to communicate symbols.